Sedimentation in Response to Glacial Retreat in Icy Bay from Late Holocene to Present.

Glaciers in Icy Bay, coastal southeast Alaska, have receded at variable rates since the Little Ice Age (LIA). Since the LIA, rain has increasingly dominated over snow in annual precipitation records for this area, resulting in less snow contribution to glaciers. We aim to characterize modern glacial retreat and the evolution of sedimentation and ice dynamics as the glacial systems separated and retreated out of Icy Bay into adjacent fjords. As the Icy Bay glacial system receded it separated into three independent glaciers, Tyndall, Yahtse and Guyot, and exposed four additional fjords, Taan, Yahtse, Guyot and Tsaa. Previous seismic imaging shows that three seismic facies dominate Taan Fiord: (1) a laminated, semi-transparent layer; (2) a hummocky, chaotic facies; (3) a laminated and hummocky facies. These facies represent distal glacimarine sediments, ice-proximal sediments, and fan delta complexes, respectively. We acquired sparker-source high-resolution seismic reflection data in Icy Bay and Taan Fiord and use a trio of predictive deconvolutions to remove the suite of acquisition artifacts including the bubble pulse and ghosts. The dataset is an improvement over older imaging in the area, with higher fold and deeper imaging, and with a larger, denser survey footprint that reaches closer to the modern ice fronts than previous studies. We will map the Taan Fiord seismic facies identified in previous studies into Icy Bay to generate a seismic characterization of bay sedimentation. Icy Bay receives input from multiple tidewater glaciers at different locations that vary in distance to any one point in the bay. Distance from the sedimentary source plays a key role in the creation of the observed seismic facies in Taan Fiord. We will use the Taan Fiord facies model in an attempt to account for mixing of multiple sediment sources, and the extent of dominance of different glacial sediment sources throughout the bay.